To manufacture semi-conductor devices which include a non-conducting substrate upon which circuitry is printed upon one or both opposite faces thereof and to which leads are to be connected by solder to terminals usually along the edges of said substrate, lead frames arranged in strips of indeterminate length are provided with such leads and heads also are on one end of such leads in parallel rows for connection to said substrate. One example of such strips of lead frames comprise the subject matter of applicant's co-pending application, Ser. No. 648,972, filed Sep. 10, 1984. For purposes of constantly tending to minimize the sizes of such substrates, the industry tends to form and arrange the terminals of the circuits on said substrates in ever closer relationship, thus posing a problem relative to depositing the necessary globules or dots of solder upon the substrate immediately adjacent the heads which are to be connected by solder to said terminal.
At present, and heretofore, where the spacing between the terminals on the substrate permitted the use of tubular dispensers in close relationship to each other, the still closer spacing of the terminals as now desired, substantially eliminates the use of tubular dispensers in view of the wall thicknesses of the same, even in closely arranged relationship. Hence, the industry has now introduced dispensing dies in which holes of minute diameter are provided therein in very closely spaced relationships, and examples of the same are somewhat illustrated in prior U.S. Pat. Nos. 4,295,596 to Doten et al, dated Oct. 20, 1981 and 4,515,297 to Schoenthaler et al, dated May 7, 1985.
The prior art also discloses means for forming small dots of solder and other similar materials, such as those of a viscous nature, and examples of attempted solutions to such discharge problems comprise the subject matter of prior U.S. Pat. Nos. 3,970,222 to Duffield, dated July 20, 1976; 4,030,640 to Citrin et al, dated June 21, 1977; and 4,154,379 to Schermutzki, dated May 15, 1979.
At present, it is common to use manufactured solder paste furnished commercially in tubes of different sizes and in which infinitely small chips of commonly used metal, such as tin for example, are mixed with a suitable carrier to produce a a viscous paste which, hopefully, is of uniform character between different manufactured batches thereof. Unfortunately, this is not always a fact and, hence, problems are presented in delivering such paste in suitable sizes useful in soldering operations relative to very closely spaced terminals of the circuits of substrates of the type to which the present invention pertains, in order that suitable spacing between adjacent terminals and soldered heads will exist in finished products. The present invention is directed to a solution of the problems now existing in the formations of adequate, closely spaced soldered connections between the heads of leads and terminals on the circuits on substrates, details of which are set forth below.